1. Field of the Invention
The present invention relates to an image processing method for illegal use of a digital image by embedding therein certain information such as electronic watermark information, an image processing apparatus and an image processing system such as a video camera utilizing such image processing method, and a computer readable memory medium storing process steps for executing such image processing method.
2. Related Background Art
The recording and reproduction of an image has conventionally be achieved by an analog video tape recorder (VTR) utilizing a recording medium on which the image signal is recorded in analog format (hereinafter called analog medium).
However, the image recorded on an analog medium is deteriorated in quality as the copying is repeated.
It has therefore become common, in recent years, to execute the image recording and reproduction with a VTR of digital type utilizing a recording medium on which the image is recorded in digital format (hereinafter called digital medium).
The image recorded on a digital medium has features of being not deteriorated in quality even after repeated copying, being easily handled on a computer and being easily transmitted through a communication line, but may cause illegal use of copyright because the unlawful copying or use can be easily achieved.
For preventing such illegal copying or use, there is known a method of embedding electronic watermark information into the image.
Such electronic watermark embedding method employs the digital ID information indicating for example the copyright owner of the image, the publication source of the image, the management number of the image, the distribution channel of the image etc. as the electronic watermark information, and mixes such electronic watermark information in the image in such a manner that such information is invisible to the user observing the image and that the source or channel of distribution of the illegally used image can be confirmed afterwards. In such information mixing, it is important that the electronic watermark information alone cannot be extracted from the image in which the electronic watermark information is embedded.
In such electronic watermark embedding method, the general user cannot see the content of the electronic watermark information, because such method is so constructed that the user cannot see whether the electronic watermark information is present in the image or the content of the electronic watermark information itself.
In certain cases, however, it is unnecessary to conceal all the content of the electronic watermark information and a part of the content may or should be made open to the general user.
In such case, the electronic watermark information has been disclosed to the user by embedding the watermark information visible to the user in the image whereby the user is rendered possible to display such information.
Such method has however been associated a drawback that such visible electronic watermark information can be removed relatively easily from the image in which such watermark information is embedded.
An object of the present invention is to solve the above-described drawbacks individually or entirely.
Another object of the present invention is to provide an image processing method capable of embedding specified visible information in an image in a not easily removable manner, an image processing apparatus and an image processing system utilizing such image processing method, and a computer readable memory medium storing the process steps for realizing such image processing method.
The above-mentioned objects can be attained, according to a first invention, by an image processing method for embedding specified information in a digital image, comprising a first embedding step of embedding first specified information in the digital image, and a second embedding step of embedding second specified information in the digital image in which the first specified information is embedded by the first embedding step.
Still another object of the present invention is to obtain respectively different embedding levels for plural embedded information.
Still another object of the present invention is to provide a novel information embedding method, an apparatus and a medium therefor.